1. Field of the Invention
The present invention relates to a process for preparing o-(carboalkoxy)phenylmethanesulfonyl chloride derivatives and more particularly, to a novel process for preparing o-(carboalkoxy)phenylmethanesulfonyl chloride expressed by the following formula 1, having a lactone compound as a starting material which is cyclic ester compound, and o-(chloromethyl)benzoyl chloride, o-(chloromethyl)benzoic acid ester derivatives and o-(carboalkoxy)phenyl methanethiosulfonic acid salt as intermediates, which is an important compound for the synthesis of sulfonyl urea herbicide. ##STR2##
wherein:
X represents hydrogen; halogen; C.sub.1.about.C.sub.6 alkyl group; C.sub.1.about.C.sub.6 halloalkyl group; C.sub.1.about.C.sub.6 alkoxy group; C.sub.1.about.C.sub.6 alkoxycarbonyl group; nitro group; or phenyl group; PA1 R represents C.sub.1.about.C.sub.6 alkyl group; C.sub.1.about.C.sub.6 halloalkyl group; or C.sub.3.about.C.sub.6 cycloalkyl group; PA1 n represents 1 to 4 as number of substituents. PA1 A lactone compound, a cyclic ester compound, is reacted with thionyl chloride(SOCl.sub.2) in the presence of Lewis acid and quaternary-ammonium salt catalyst to prepare carbonyl chloride compounds in a high yield at a lower temperature; PA1 An alcohol compound, a reacting material and solvent, is reacted with the above intermediate compound, so prepared, for esterification in an easier procedure and under a mild condition, thus preparing o-(chloromethyl)benzoic acid ester derivatives; PA1 The reacting mixture is further reacted with less-toxic thiosulfonic acid salt instead of using thiourea having carcinogenic potential, followed by chlorination to obtain o-(carboalkoxy)phenylmethanesulfonyl chloride derivatives as a final product expressed by the formula 1. PA1 a) A lactone compound of the following formula 2 is reacted with thionyl chloride(SOCl.sub.2) in the presence of Lewis acid and quaternary-ammonium salt catalyst to prepare a o-(chloromethyl)benzoyl chloride of the following formula 3; PA1 b) A compound of the above formula 3 is esterified in alcohol compound as a reacting material and solvent to prepare a o-(chloromethyl)benzoic acid ester derivatives of the following formula 4; PA1 c) A compound of the above formula 4 is reacted with thiosulfonic acid salt to prepare a o-(carboalkoxy)phenylmethanethiosulfonic acid salt of a following formula 5; and PA1 d) A compound of the above formula 5 is chlorinated to prepare a o-(carboalkoxy)phenylmethanesulfonyl chloride derivative of the following formula 1. ##STR4## PA1 X represents hydrogen, halogen, C.sub.1.about.C.sub.6 alkyl group, C.sub.1.about.C.sub.6 halloalkyl group, C.sub.1.about.C.sub.6 alkoxy group, C.sub.1.about.C.sub.6 alkoxycarbonyl group, nitro group or phenyl group; PA1 R represents C.sub.1.about.C.sub.6 alkyl group, C.sub.1.about.C.sub.6 halloalkyl group or C.sub.3.about.C.sub.6 cycloalkyl group; PA1 n represents an integer of 1 to 4 as number of substituents.
2. Description of the Prior Art
The o-(carboalkoxy)phenylmethanesulfonyl chloride derivatives, represented as the above formula 1, are described as essential raw materials for synthesis of sulfonyl urea herbicide (U.S. Pat. No. 4,420,325 and Germany Publishment No. 3,927,788).
The conventional process for synthesizing o-(carboalkoxy)phenylmethanesulfonyl chloride derivatives expressed by the formula 1 has been reported in the U.S. Pat. No. 4,420,325 and Hauxue Shijie 31 211(1990)(CA 114 101, 765). The process is summarized in the following Scheme 1. ##STR3##
According to the conventional process of the above Scheme 1, o-(chloromethyl)benzoic acid methyl ester and thiourea are reacted for the synthesis of isothiouronium salt as an intermediate and then, the intermediate is chlorinated to prepare phenylmethanesulfonyl chloride as a final product. However, in light of the fact that thiourea designed for the synthesis of isothiouronium salt is a potential carcinogenic material, its industrial application on a mass scale is not easily made available.
Further, the method for preparing the o-(chloromethyl)benzoic acid methyl ester, used as a starting material in Scheme 1, is disclosed in some patent specifications. For example, he methyl group of side chain of the o-methylbenzoic acid methyl ester is chlorinated by reaction of chlorine and hydrogen chloride gas, simultaneously with UV radiation, as described by U.S. Pat. No. 4,689,425. However, this method has generated a lot of by-products, in spite of the fact that the reaction is terminated at the 10% level to the remaining initial substance. Thus, the method has a difficulty in purifying a final product, let alone a low yield.
Also, according to another method of preparing o-(chloromethyl)benzoyl chloride, described in U.S. Pat. No. 5,504,249, phthalide and thionyl chloride are reacted in the presence of an organic nitrogen compound and hydrogen chloride catalyst at 160.about.170.degree. C., thereby obtaining the final compound. However, this method has recognized some disadvantages in that the reaction is not easily made available in a conventional reactor due to the boiling point of the thionyl chloride and hydrogen chloride at 79.degree. C. and -85.degree. C., respectively. Thus, the method may not easily be applied to the industrial process.
Another methods for preparing chlorine-substituted carboxylic acid chloride via reaction between a lactone compound with phosgen has been disclosed; hence, a catalyst includes pyridine(U.S. Pat. No. 2,778,852), quaternary ammonium salt(U.S. Pat. No. 4,764,309) or phosphine oxide(EP Patent No. 413, 264). However, these methods have some disadvantages in that the reaction should be performed using phosgen having a boiling point 8.degree. C. at more than 120.degree. C. Furthermore, since phosgen is very toxic, the process is very dangerous in its gaseous state.
To overcome the above shortcomings, the inventor et al. have endeavored to develop a preparing process useful for the industrial mass production of a compound expressed by the formula 1.